1. Field of the Invention
This invention relates generally to detectors such as ultrasonic motion detectors and, in particular, to techniques for testing such ultrasonic detectors used as occupancy sensors for detecting motion in rooms.
2. Description of the Prior Art
Motion detectors, such as ultrasonic motion detectors, are used to detect the motions of people and things, moving in fixed environments, such as rooms and hallways. Such conventional detectors operate by flooding the environment to be monitored with transmitted and reflected ultrasonic energy and then detecting changes in the resultant steady state ultrasonic energy reception pattern observed by the detector from the monitored environment in order to sense changes caused by the motions of the people or things to be monitored. Conventional detectors tend to be sensitive to changes in ambient conditions, such as changes in temperature and even air densities, that interfere with their ability to accurately detect minor motions intended to be monitored. When used as occupancy detectors, for example, the detectors must be sufficiently sensitive to detect minor motions, such as the movement of a human arm through a specified arc or to reach a telephone or turn a page, without falsely being triggered by other events such as changes in the ambient conditions or motions observable through a door way or open window.
Conventional techniques for testing such detectors require the use of rooms and hallways of the same approximate size as the rooms and hallways in which such detectors are intended to be used. Such testing rooms usually must be isolated so that unintentional disturbances, such as changes in air currents or even workers walking by, don't interfere with tests in progress. These isolated testing rooms are expensive and inconvenient, particularly for use in high quality control production systems in which all of the detector units are tested in an operating environment before delivery.
In addition to the physical and other inconveniences of an isolated testing room, the testing procedures used in such rooms are difficult to accurately and repeatably replicate. To fully duplicate the testing of a particular model of sensor for each unit manufactured would, for example, require the same sized person to walk through the same room in the same way for each sensor being tested. This is impractical to achieve in a manufacturing environment.
It is common to test such sensors to verify the minimum range of motion required to trigger the sensor. A typical test might therefore require that a specified minor motion, such as a particular arm movement, be sufficient to trigger the detector while a smaller motion will not. A larger motion, such as a person walking, must always trigger the detector. To test each detector, the same minor and major motions must accurately and repeatably be applied to each device in the same environment and the detector output recorded. This has in the past been prohibitively expensive and time consuming and has lead manufacturers to test such sensors for electronic or other functional operation and only, at best, test selected units in the operating environment.
What are needed are practical, more convenient techniques suitable for the accurate and repeatable testing of such detectors in their operating environments so that all such detectors may be tested for quality control purposes.